Clear fuel filter

[84E24]

I have a clear fuel filter on my 73 cs, stock motor with dual Webbers.

Issues: after setting for about a week (or less ) it is very hard to get started. I have to use strarter fluid and finally it starts. The filter shows no gas when I start cranking but by the time it starts it is full. After it starts there is no problems starting. The tail pipe does have black soot in it.

What I have done: replaced the suction device and o-ring. I do get a strong vacume sound when I open the gas cap.

Questions: 1) to me it sounds like the carb. bowls are draining empty??
2) the fuel in the filter and lines are draining back into the tank??
3) should there be fuel stored in the fuel pump to start the next time?

So, there is no fuel to start the car until it is sucked up again.
Is this normal or when the engine is turned off the gas in the bowls stays there, fuel in the fuel pump and the fuel in the filter and hose stay full.

Do I need to add a check valve after the filter to keep the gas from running backwards?
or rebuild the fuel pump?

Any help will help.

Thanks,

Steve

 

[Tom M]

Steve:
Another possibility is that the fuel pump is sucking air. To test, disconnect the fuel pump output and redirect it to a clean two litre soda bottle. Correctly defeat the ignition and then crank to see how long it takes to have fuel output.
If there is a significant delay, you can diagnose the failure with a vacuum/pressure gauge, a couple lengths of fuel line and a tee. A hand operated vacuum pump is handy, but use the brake bleeder bottle so you don't suck fuel through the pump and damage it's seals.
I have had the short piece of hose at the fuel tank sending unit go porous.
tom

 

[HB Chris]

Fuel Pump

I had this problem on my 2002 two months ago, fuel bowl would be empty after 1 or 2 weeks. Car would crank and crank but not much fuel appeared in the clear filter. I used a hand pump and I got fuel instantly. I replaced the pump and problem was solved. The pump diaphragm, I believe, allowed fuel to drain back and was not strong enough to pull sufficient volume until it was finally running, which took forever. I hear the coupe fuel pumps have gone way up in price, no rebuild kit is available for the early style pumps either (I may be wrong), only Pierburgs which need an 8mm intake and output. Hope this helps.